Saturday features season-defining games for several conferences. The Big 12 has two games between undefeated teams, starting with the Red River Shootout and ending with Oklahoma State-Missouri. Texas, Oklahoma and the Tigers will battle for position in the national championship race. Quarterbacks Chase Daniel, Colt McCoy and Sam Bradford will look for separation in the Heisman race, and Oklahoma State is looking for a little more respect.

In the SEC, LSU looks to strengthen its case for the national title after losing ground to Missouri last week. The Tigers face a Florida team that is hoping to stay in the SEC race.

When: Noon
TV: ABC
Broadcasters: Brent Musburger play-by-play, Kirk Herbstreit analyst
Line: Oklahoma by 6.5 Why you should watch: Both are ranked in the top five for the first time since 2004 and for the fourth time in the Mack Brown-Bob Stoops era. Oklahoma has won the past three matchups when both teams were in the top five. Quarterbacks Sam Bradford and Colt McCoy have combined to throw for 2,945 yards and 34 touchdowns, while completing more than 75 percent of their passes. Also keep an eye on Texas defensive end Brian Orakpo (5.5 tackles for a loss, two forced fumbles) against a stout Oklahoma offensive line.

When: 3:30 p.m.
TV: ABC regional/ESPN GamePlan
Broadcasters: Brad Nessler play-by-play, Bob Griese and Paul Maguire analysts
Line: North Carolina by 7
Why you should watch: The Irish and the Tar Heels, both 4-1, have turned around their fortunes. Notre Dame already has exceeded its 2007 win total; UNC can do the same with a win against the Irish. The game could be decided by a Tate. North Carolina's Brandon Tate is third in the country with 194.6 all-purpose yards per game. Notre Dame's Golden Tate leads the Irish with 397 receiving yards and three touchdowns. Or it could be decided by North Carolina linebacker Bruce Carter, who blocked three consecutive punts Saturday against Connecticut, giving him four blocks in the past two games.

When: 8 p.m.
TV: CBS
Broadcasters: Verne Lundquist play-by-play, Gary Danielson analyst
Line: Florida by 4
Why you should watch: A loss to Ole Miss two weeks ago means Florida basically faces a must-win game if its wants to stay in the SEC race. LSU slipped behind Missouri in the national rankings but could move back up if redshirt freshman quarterback Jarrett Lee can win in The Swamp. If history is any indication, get ready for a low-scoring affair. CBS has been the "Can't Buy Scoring" network. Florida is the only team in a CBS game of the week that has scored more than two touchdowns: Alabama beat Kentucky 17-14, Auburn beat Tennessee 14-12, Florida beat Tennessee 30-6 and Georgia beat South Carolina 14-7 on CBS this season.

When: 8 p.m.
TV: ESPN
Broadcasters: Mike Patrick play-by-play, Todd Blackledge analyst
Line: Penn State by 4.5
Why you should watch: One-loss teams in the Big Ten – and both participants in the 3:30 p.m. Michigan State-Northwestern game in particular – will be pulling for an upset. Penn State is the Big Ten's most legitimate national championship contender. While the Nittany Lions have been one of the nation's biggest surprises, Wisconsin has been one of the biggest disappointments. The Badgers are in danger of falling to 0-3 in the Big Ten, but they easily could be 2-0 and a top-10 team. Wisconsin led in the fourth quarter against Michigan and Ohio State before squandering the leads.

When: 8 p.m.
TV: ESPN2
Broadcasters: Mark Jones play-by-play, Bob Davie analyst
Line: Missouri by 13.5
Why you should watch: It's the second game of this week's Big 12 "Big Weekend" doubleheader. Oklahoma State lags behind its Big 12 South brethren in publicity, but its record is unblemished and its offense is dangerous. While the rest of the Big 12 is obsessed with the passing game, the Cowboys are second in the nation in rushing behind tailback Kendall Hunter (708 yards, eight touchdowns). With that running game, Oklahoma State has topped 50 points in its past four games (against Houston, Missouri State, Troy and Texas A&M). Missouri is allowing just 95 rushing yards per game. But is that because the Tigers' front seven is strong or because opponents get so far behind so quickly that they are forced to throw?

David Fox is a national writer for Rivals.com. He can be reached at dfox@rivals.com.